1. Field of the Invention
The instant invention relates to methods of and apparatus for testing internal combustion engines. More particularly, the instant invention relates to electronic testers which monitor the cooling systems of liquid cooled, internal combustion engines to locate malfunctioning components therein.
2. Technical Considerations and Prior Art
The proper function of cooling systems is necessary for proper functioning of internal combustion engines. The usual course of cooling system malfunction is a faulty thermostat, however, the malfunction can also be a clogged block or radiator, or a faulty clutch fan or a faulty automatic electric fan.
Considering thermostats first, in internal combustion engines, thermostats are essential to the engine's proper performance since the thermostat controls an engine's temperature. When an engine is operated too cold, excessive condensation, sludge formation, hesitation and poor fuel economy may occur. If the engine is operated at too high a temperature, there is a danger of premature ignition, stumbling, burned valves and perhaps serious damage to pistons, cylinders and other vital engine parts.
Thermostats are very simple, inexpensive automotive parts which are readily removable from the cooling system of an engine. Accordingly, the general method of testing thermostats is to first remove the thermostat from the engine and thereafter place the thermostat in a container of water in which there is also a thermometer. The container of water is heated to the rated temperature of the thermostat and the thermostat is visually inspected to see if it has opened at the rated temperature. This is, of course, a cumbersome and time consuming procedure which requires considerable time and effort. Accordingly, the mechanics and do-it-yourself automobile owners simply replace a thermostat if there appears to be difficulty with an engine's cooling system. However, the thermostat may not be the cause of overheating or cold operating temperatures and the thermostat may have been replaced needlessly while the problem still persists. In addition, the currently used test does not test the thermostat under engine operating conditions. Accordingly, the test is not necessarily accurate.
Testing the cooling systems and thermostats of heavy-duty equipment, such as buses, bulldozers, etc., is even more time consuming, difficult and costly than testing passenger cars in that it frequently takes two and one-half to six hours or more to complete a test.
The prior art has recognized the deficiencies in the aforementioned test method and attempts have been made to provide devices for testing thermostats while the thermostats are still installed in engine cooling systems. U.S. Pat. Nos. 3,262,314 and 4,069,712 are exemplary of these approaches. Considering U.S. Pat. No. 3,262,314, first it is seen that this patent utilizes an obsolete bridge circuit to analyze temperature data from the engine. Moreover, the display is rather inconvenient to interpret and requires considerable mental effort. In addition, the device of this patent requires one to hook two temperature sensors to the automobile engine rather than one. Finally the testing device is not necessarily simply operated from the automobile's battery.
U.S. Pat. No. 4,069,712 issued to Armstrong et al and assigned to United Technologies Corporation discloses a complex, expensive computerized thermostat tester in which it is necessary to coordinate engine speed and pressure readings with temperature readings in order to test an engine's thermostat. This is obviously an expensive and perhaps unreliable system which requires considerable skill to utilize. The expense of the device disclosed in U.S. Pat. 4,069,712 places it beyond the needs or reach of the small repair shop or do-it-yourselfer.
Cooling system problems can also result from a clogged block or defective radiator. The prior art does not disclose a system which tests for these defects, as well as a defective thermostat. Modern engines utilize either clutch fans or automatic electric fans to cool liquid coolant in the radiators of the engines. The prior art does not disclose a system which can also test for defective fans during a thermostat test.
Accordingly, there is a need for an electronic thermostat tester which is accurate, very inexpensive, easy to use and reliable.